Plasticized semicrystalline polyamide molding compositions, and in particular, those compositions based on PA11 or PA12, have long been used as extruded pipes in automotive construction, since these compositions have excellent mechanical strength and chemicals resistance. However, the extruded and molded products stiffen after a short use period at the high temperatures, which are increasing in engine applications. This stiffening is attributed to the volatility of the external plasticizers. In addition, when the extruded products are exposed to pressure, they have a tendency toward irreversible deformation at increased temperatures of 110 to 150° C. Although these disadvantages can be avoided by using molding compositions based on higher-melting polyetheresteramides, for example as described in EP-A-0 095 893, this class of polyamide elastomer is unsuitable for producing pipes usable for the abovementioned applications, since, in relation to hydrolysis resistance, these molding compositions fall far short of the resistance of traditional polyamide molding compositions, and fail after just a few weeks.